Computational Fluid Dynamics software packages for room modal behavior modelling

AudioExplorations · Apr 12, 2012

Does anyone here use computational fluid dynamics software packages to model modal behavior of listening rooms? I am looking for a good, easy to use package that has standard modules for sound radiators that I can drop in a meshed 3D model of my listening room, apply material properties to floors, walls, and then run simulations.

I would like to determine the optimal location of subwoofers in my listening room and generate simulations such as the following (taken from here):

Steve Williams · Apr 12, 2012

Keith is the only one I am aware of who uses it

amirm · Apr 12, 2012

The problem is not identifying CFD programs. They are commercially available although not cheap at all. I think the software Keith uses has a license fee north of $50,000. It also requires a skilled operator to program the design into it or it won't "converge." That is a term we use when a numerical solution of a physical simulation cannot generate a final answer. In this case, Keith uses a PhD researcher to make it work.

The bigger issue is that CFD is just going to tell you the pressure in the room. Those graphs you see and the analysis of what is "good sound" relative to countless other iterations is piece of proprietary software that Keith has integrated with the commercial CFD software.

Currently the solution exists as a service through Kieth Yates. It is rather expensive (around $10,000). Keith hopes to get the price down at some point but that is where it is at today.

AudioExplorations · Apr 12, 2012

amirm said:
The problem is not identifying CFD programs. They are commercially available although not cheap at all. I think the software Keith uses has a license fee north of $50,000. It also requires a skilled operator to program the design into it or it won't "converge." That is a term we use when a numerical solution of a physical simulation cannot generate a final answer. In this case, Keith uses a PhD researcher to make it work.

The bigger issue is that CFD is just going to tell you the pressure in the room. Those graphs you see and the analysis of what is "good sound" relative to countless other iterations is piece of proprietary software that Keith has integrated with the commercial CFD software.

Currently the solution exists as a service through Kieth Yates. It is rather expensive (around $10,000). Keith hopes to get the price down at some point but that is where it is at today.

I am hoping something like the open source OpenFoam CFD software is sufficient.

I have alot of experience in 3D modelling and simulation so I hope to be able to get a usable result. Absolute SPL values are not important, I simply would like to simulate how different sub positions excite different room modes and then through a manual iteration (based on common rules of sub placement) find locations that result in minimal modal excitement at the listening position.

Ultimately I would like to develop an online tool (something like the hunecker.de tool) to help determine optimal locations based on the inputted room dimensions.

amirm · Apr 12, 2012

Ah, didn't realize you knew the field. I hope my post did not come across as too pedantic

.

amirm · Apr 12, 2012

BTW, can talk more about hunecker.de tool? Where did it come from?

AudioExplorations · Apr 12, 2012

Just came across it through a google search. I have been using the Room Eigenmodes tool a lot, I find this to be the best way to visualize problematic room modes. My room measurements match up very well with the axial modes displayed in the tool. This really helps to understand your room and to give 'usable' indications of subwoofer positioning (i.e. in the modes, anti-modes, in between, etc).

Steve Williams · Apr 12, 2012

jdebonth said:
Just came across it through a google search. I have been using the Room Eigenmodes tool a lot, I find this to be the best way to visualize problematic room modes. My room measurements match up very well with the axial modes displayed in the tool. This really helps to understand your room and to give 'usable' indications of subwoofer positioning (i.e. in the modes, anti-modes, in between, etc).

microstrip from Portugal has posted that link here as well. Thanks also

DonH50 · Apr 12, 2012

Comsol (think that's the name). Does a lot with IEEE and has various acoustic modelling packages.

AudioExplorations · Apr 13, 2012

Looks good. Comsol has an acoustics module and even example models setup including one that computes room eigenmodes. This should get me started.

Thanks for the tip!

AudioExplorations · Apr 13, 2012

There are also some software packages custom built for acoustic modelling, such as Odeon

Nyal Mellor · Apr 16, 2012

Look at ABEC by RandTeam http://www.randteam.de/Abec2/Index.html...I think the EASERA guys may release some commercial software soon if their recent NY AES paper with WSDG was anything to go by ...last link on http://www.aes.org/events/131/papers/?ID=2804. Not CFD but similar (BEM). Jeff and I use ABEC.

Mike · Apr 16, 2012

Exactly what does one do with this software? Make a collection of observations and then fit the data to a model (or is it Navier–Stokes equations?) and then use numerical methods to obtain a solution. If the goal is modelling and simulation, do you build a model and then simulate answers to what if questions?

Sorry for the naivety.

Mike

kevinh · Apr 16, 2012

Mike said:
Exactly what does one do with this software? Make a collection of observations and then fit the data to a model (or is it Navier–Stokes equations?) and then use numerical methods to obtain a solution. If the goal is modelling and simulation, do you build a model and then simulate answers to what if questions?

Sorry for the naivety.

Mike

The software would allow one to determine (at least) how many and where to place SW speakers and room treatements to
achieve design goals prior to purchasing eq, installing anything, and going on site to measure th room and then make
adjustments. This would involve doing 'what if' simulations. It can (if used properly) deal with irregular rooms that would be difficult to deal
with using trial and error.

It maximizes what one can do without using electronic room correction. Making the job of any ERC much easier.

Mike · Apr 16, 2012

kevinh said:
The software would allow one to determine (at least) how many and where to place SW speakers and room treatements to
achieve design goals prior to purchasing eq, installing anything, and going on site to measure th room and then make
adjustments. This would involve doing 'what if' simulations. It can (if used properly) deal with irregular rooms that would be difficult to deal
with using trial and error.

It maximizes what one can do without using electronic room correction. Making the job of any ERC much easier.

Thanks, kevinh.

It seems to me that optiimizing speaker positions and treatments' positions is like estimating unknown model parameters (like using maximum likelihood in non-linear regression). I wonder what the theory is behind this software.

Mike

kevinh · Apr 16, 2012

Here is an article at wiki giving some background:

http://en.wikipedia.org/wiki/Computational_fluid_dynamics

amirm · Apr 16, 2012

kevinh said:
Here is an article at wiki giving some background:

http://en.wikipedia.org/wiki/Computational_fluid_dynamics

The link brings back fond memories. In the 1980s I was working for a "minisupercomputer" company. I took a job to get super computing apps ported to it. Next thing I know, I am getting every numerical application you can imagine, from fluid dynamics to finite element and megnetic flow. I could not even spell these things let alone figure out why our computer was spitting out code that would not run. And when they did run, there would be a massive files full of wrong results. It was a lot of fun getting things working without understanding what they did or how they really worked! Towards the end though, I learned my way around and got familiar with terms like Navier Stokes and Euler equations. Fun days those were....

Mike · Apr 17, 2012

kevinh said:
Here is an article at wiki giving some background:

http://en.wikipedia.org/wiki/Computational_fluid_dynamics

Thanks again!

Computational Fluid Dynamics software packages for room modal behavior modelling

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